1. Field of the Invention
This invention relates to a flat panel display device, and more particularly to a plasma display panel that is capable of improving the discharge efficiency and the brightness. Also, the present invention is directed to a method of driving said plasma display panel.
2. Description of the Related Art
Generally, a plasma display panel (PDP) radiates a fluorescent body by an ultraviolet with a wavelength of 147 nm generated during a discharge of He+Xe or Ne+Xe gas to thereby display a picture including characters and graphics. Such a PDP is easy to be made into a thin film and large-dimension type. Moreover, the PDP provides a very improved picture quality owing to a recent technical development. The PDP is largely classified into a direct current (DC) driving system and an alternating current (AC) driving system. The DC-type PDP causes an opposite discharge between an anode and a cathode provided at a front substrate and a rear substrate, respectively to display a picture. On the other hand, the AC-type PDP allows an alternating voltage signal to be applied between electrodes having dielectric layer therebetween to generate a discharge every half-period of the signal, thereby displaying a picture. Since such an AC-type PDP uses a dielectric material which allows a wall charge to be accumulated on the surface thereof upon discharge, it produces a memory effect.
Referring to FIG. 1, the AC-type PDP includes a front substrate 1 provided with a sustaining electrode pair 10, and a rear substrate 2 provided with an address electrode 4. The front substrate 1 and the rear substrate 2 are spaced in parallel to each other with having barrier ribs 3 therebetween. A mixture gas, such as Nexe2x88x92Xe or Hexe2x88x92Xe, etc., is injected into a discharge space defined by the front substrate 1, the rear substrate 2 and the barrier ribs 3. The sustaining electrode 10 makes a pair by two within a single of plasma discharge channel. Any one of the sustaining electrode pair 10 is used as a scanning/sustaining electrode that responds to a scanning pulse applied in an address interval to cause an opposite discharge along with the address electrode 4 while responding to a sustaining pulse applied in a sustaining interval to cause a surface discharge with the adjacent sustaining electrodes 10. Also, the remaining one of the sustaining electrode pair 10 is used as a common sustaining electrode to which a sustaining pulse is applied commonly. On the front substrate 1 provided with the sustaining electrodes 10, a dielectric layer 8 and a protective layer 9 are disposed. The dielectric layer 8 is responsible for limiting a plasma discharge current as well as accumulating a wall charge during the discharge. The protective film 9 prevents a damage of the dielectric layer 8 caused by the sputtering generated during the plasma discharge and improves the emission efficiency of secondary electrons. This protective film 9 is usually made from MgO. The barrier ribs 3 for dividing the discharge space are extended perpendicularly at the rear substrate 2. On the surfaces of the rear substrate 2 and the barrier ribs 3, a fluorescent material 5 excited by a vacuum ultraviolet lay to generate a visible light is provided.
In such an AC-type PDP, one frame consists of a number of sub-fields so as to realize gray levels by a combination of the sub-fields. For instance, when it is intended to realize 256 gray levels, one frame interval is time-divided into 8 sub-fields. Further, each of the 8 sub-fields is again divided into a reset interval, an address interval and a sustaining interval. The entire field is initialized in the reset interval. The discharge pixel cells on which a data is to be displayed are selected by the address discharge in the address interval. The selected discharge pixel cells sustain the discharge in the sustaining interval. The sustaining interval is lengthened by an interval corresponding to 2n depending on a weighting value of each sub-field. In other words, the sustaining interval involved in each of first to eighth sub-fields increases at a ratio of 20, 21, 23, 24, 25, 26 and 27. To this end, the number of sustaining pulses generated in the sustaining interval also increases into 20, 21, 23, 24, 25, 26 and 27 depending on the sub-fields. The brightness and the chrominance of a displayed image are determined in accordance with a combination of the sub-fields. However, the three-electrode, AC surface-discharge PDP has problems in that, since a voltage required for the sustaining discharge is high, the power consumption is large and that the discharge and light-emission efficiency upon sustaining-discharge between the sustaining electrode pair is low.
In order to solve these problems of the three-electrode, AC surface-discharge PDP, there has been suggested a PDP provided with four sustaining electrodes.
Referring to FIG. 2 and FIG. 3, the conventional five-electrode PDP includes a sustaining electrode pair 13 and 16 and a trigger electrode pair 30 and 36 formed on a front substrate 20, and an address electrode 17 formed on a rear substrate 18. The trigger electrode pair 30 and 36 is provided between the sustaining electrode pair 13 and 16 to cause a trigger discharge by a wall voltage produced upon address-discharge and an application voltage, thereby initiating a sustaining electrode. The sustaining electrode pair 13 and 16 forms a pair within a single plasma discharge channel. Any one of the sustaining electrode pair 13 and 16 is used as a scanning/sustaining electrode that responds to a scanning pulse applied in an address interval to cause an opposite discharge along with the address electrode 17 while responding to a sustaining pulse applied in a sustaining interval to cause a surface discharge with the adjacent sustaining electrode 13 or 16. Also, the remaining one of the sustaining electrode pair 13 and 16 is used as a common sustaining electrode to which a sustaining pulse is applied commonly. The sustaining electrode pair 13 and 16 causes a sustaining discharge by a wall voltage formed by the trigger discharge generated between the trigger electrode pair 30 and 36 and an application voltage. The sustaining electrode pair 13 and 16 and the trigger electrode pair 30 and 36 have a line width smaller than transparent electrodes 28 and 34 and includes metal bus electrodes 26 and 32 formed at one edge of the transparent electrodes 28 and 34, respectively. A dielectric layer 23 and a protective layer 24 are disposed on the front substrate 20 to cover the sustaining electrode pair 13 and 16 and the trigger electrode pair 30 and 36. Wall charges produced upon plasma display are accumulated in the dielectric layer 23. The protective film 24 prevents a damage of the dielectric layer 23 caused by the sputtering generated during the plasma discharge and improves the emission efficiency of secondary electrons. Barrier ribs 25 and a fluorescent material 22 are formed on the rear substrate 18 provided with the address electrode 17.
When the sustaining electrode pair 13 and 16 of the five-electrode PDP is compared with the sustaining electrode pair 10 of the three-electrode PDP, a distance between the sustaining electrode pair 13 and 16 is longer than that between the electrode pair 10. Thus, the five-electrode PDP has a better light-emission efficiency than the three-electrode PDP upon discharge.
However, as shown in FIG. 4, the five-electrode PDP concentrates the sustaining discharge upon the middle portion of the discharge cell. The PDP having such a structure has a problem in that only a portion of energy produced upon sustaining-discharge excites the fluorescent material. In other words, only a portion of energy produced during the sustaining discharge excites the fluorescent material while the remaining energy other than the energy exciting the fluorescent material emerges an excessive current flowing the electrodes. As a result, the PDP has a large power consumption and a low discharge and light-emission efficiency.
Accordingly, it is an object of the present invention to provide a plasma display panel and a driving method thereof that are capable of improving the discharge efficiency as well as the brightness.
In order to achieve these and other objects of the invention, a plasma display panel according to one aspect of the present invention includes an auxiliary electrode pair for causing an auxiliary discharge in which its area at the periphery of a discharge cell is wider than that at the center of the discharge cell; and a sustaining electrode pair arranged at each side of the auxiliary electrode pair to cause a sustaining discharge by utilizing the auxiliary discharge.
A plasma display panel according to another aspect of the present invention includes a transparent electrode formed at the sustaining electrode pair in such a manner to be separated within the discharge cell.
A method of driving a plasma display panel according to still another aspect of the present invention includes the steps of enlarging an area of an auxiliary electrode pair corresponding to the center portion of a discharge cell to concentrate wall charges on the center portion of the discharge cell during an auxiliary discharge generated between the auxiliary electrode pair; and causing a sustaining discharge between a sustaining electrode pair by utilizing the wall charges produced by the auxiliary discharge.
A method of driving a plasma display panel according to still another aspect of the present invention includes the steps of causing an auxiliary discharge between a trigger electrode pair; and simultaneously causing a plurality of sustaining discharge within a discharge cell using an auxiliary electrode pair.